/**
 * Copyright 2009-2017 the original author or authors.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.ibatis.scripting.xmltags;

/**
 * @author Clinton Begin
 */
public class IfSqlNode implements SqlNode {
	/**
	 * evaluator属性用于解析OGNL表达式
	 */
	private final ExpressionEvaluator evaluator;

	/**
	 * 保存<if>标签test属性内容
	 */
	private final String test;

	/**
	 * <if>标签内Sql内容
	 */
	private final SqlNode contents;

	public IfSqlNode(SqlNode contents, String test) {
		this.test = test;
		this.contents = contents;
		this.evaluator = new ExpressionEvaluator();
	}

	@Override
	public boolean apply(DynamicContext context) {
		// 如果OGNL表达式值为true,则调用<if>标签内容对应的SqlNode的apply（）方法
		if (evaluator.evaluateBoolean(test, context.getBindings())) {
			contents.apply(context);
			return true;
		}
		return false;
	}

}
